Thiourea organocatalysis

The scope of these small-molecule H-bond donors termed (thio)urea organocatalysis covers both non-stereoselective and stereoselective reactions.

[1] Hydrogen-bonding between thiourea derivatives and carbonyl substrates involve two hydrogen bonds provided by coplanar amino substituents in the (thio)urea.

[6] Thioureas are often found to be stronger hydrogen-bond donors (i.e., more acidic) than ureas[7] because their amino groups are more positively charged.

Quantum chemical analyses revealed that this counterintuitive phenomenon, which is not explainable by the relative electronegativities of O and S, results from the effective steric size of the chalcogen atoms.

Early contributions were made by Kelly, Etter, Jorgensen, Hine, Curran, Göbel, and De Mendoza (see review articles cited below) on hydrogen bonding interactions of small, metal-free compounds with electron-rich binding sites.

Ketone complex with Schreiner's N,N'-bis[3,5-bis(trifluoromethyl)phenyl thiourea. The double hydrogen-bonding, clamp-like binding motif is evident. ^{[

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